It’s Not You. The Heat Does Affect Your Performance

During the months of June and July, much of the world faced an unprecedented heat wave. In the case of Mexico, for example, it broke the record for registered deaths and heat strokes… and this is just the beginning.

According to World Meteorological Organization (WMO) predictions, “there is a 66% chance that, between 2023 and 2027, the global average annual near-surface temperature will exceed pre-industrial levels by more than 1.5°C for at least one year. There is a 98% chance that at least one of the next five years and the five years as a whole will be the warmest ever recorded. It is important to add that when they say “pre-industrial levels,” they refer to 1850-1900 since “it is prior to the emission of greenhouse gases from human and industrial activities.”

This means that both the next few weeks and years, records related to high temperatures are expected to be broken, and with this, the constant feeling that it is more challenging to pay attention, form thoughts, and other cognitive functions.

Also, much energy is needed to maintain body temperature and stay cool. Maintaining a constant internal temperature is vital for the body’s functioning since this process requires energy. And with sweating comes the loss of fluids and essential salts and electrolytes, such as potassium, calcium, and magnesium, leading to tiredness.

What impact does the heat have on our minds and bodies?

Joe Allen, co-director of Harvard University’s Center for Climate, Health, and the Global Environment, and several colleagues looked at students living in college dormitories during a heat wave in Boston. Half of the students lived in buildings with central air conditioning, with a temperature of 22 degrees; the other half without air conditioning, with an average temperature of 27 degrees.

“In the morning, when they woke up, we sent evidence to their cell phones,” Allen explains. The students took two tests a day for 12 consecutive days. One trial included basic addition and subtraction to measure cognitive speed and memory; another tested attention and processing speed.

The researchers found that those students without air conditioning reacted 13% slower on arithmetic tests and gave nearly 10% fewer correct answers per minute.

Ten years before Joe Allen’s study, in 2006, the Lawrence Berkeley National Laboratory discovered that worker performance began to decline when office temperatures exceeded 22 degrees, especially when it exceeded 27 degrees, where the performance of the employees dropped by 9%.

How are student learning and well-being affected by heat?

At the start of the 2022-2023 school year, several schools in the United States were forced to send students home early or close and teach remotely due to high temperatures and a lack of air conditioners. That summer marked the third-hottest summer on record in the nation, and yet those at OMM believe the worst is yet to come.

In 2021, economists R. Jisung Park and Joshua Goodman combined standardized test data from 58 countries and 12,000 US school districts with detailed weather and academic calendar information to “show that the rate of learning decreases with an increase in the number of hot school days.” This resulted in evidence that climatic differences contribute to differences in academic performance.

R. Jisung and Joshua Goodman also published research examining 10 million high school students who took the Scholastic Aptitude Test (SAT) pretest between 2001 and 2014. They found that exposure to heat decreases the productivity of instructional time. “Without air conditioning, a 1°F hotter school year reduces that year’s learning by 1 percent,” the publication reported. His research also showed that taking an exam on a 32-degree day can make the probability of passing it 10.9% lower.

An article published in Psychology Today covers the effects of heat on cognitive and executive functions, as well as memory and attention. Cognitive functions were measured through the Visual Search Task (VST), which asked participants to respond as quickly as possible to a visual cue appearing on a screen in front of them.

The portal describes the procedure: “In the simple version of the task, the triangle was a solidly outlined, bold green triangle. In the complex version of the task, the triangle was made of dots presented on a blinking background. The VST task measures the ability to filter out distracting information and interpret a particular signal.”

Executive functions were measured using Stroop, where a word is presented on the screen, and participants match it as quickly as possible. In the complex version of this task, participants were asked to indicate the font color used to present the word rather than the word itself. Some words were congruent (red with red ink), and others were incongruent (red written in green ink); this was to record reaction time along with the number of correct responses.

Memory was measured using Corsi’s block test, where “a 3 x 3 grid of squares was presented, and sequences of squares were lit up. Participants were asked to reproduce the order in which the square was lit, with sequences of lit squares increasing in length on each trial from three to nine. The three longest correctly remembered sequences were recorded,” the publication mentioned.

And finally, attention was measured using the Rapid Visual Information Processing Test (VP), where sequences of three numbers between the values of two and nine were randomly presented. Participants were asked to indicate as quickly as possible whether those sequences were odd or even while reaction time and accuracy were measured.

In addition to these tests, the participants reported their moods and subjective feelings about the heat and the tasks they were asked to perform. Their physiological responses were also measured, for example, by checking body temperature, heart rate, skin temperature, etc. Half of the participants spent an hour sitting in a room with the temperature at 39.6 degrees and the other at 21.2 degrees to gauge the impact of temperature.

Cognitive and executive function was measured again after one hour of heat exposure for both groups. They were then asked to return a week later, where the exposure conditions were changed and the study repeated.

Psychology Today reported that “both executive function and perception were affected by heat exposure,” as response times were slower after participants were exposed to heat for the Stroop and plain VST tests. Responses to the more complex part of the VST improved after exposure to high temperatures, although reaction times were slower.

For researchers, this could demonstrate what is known as the speed/accuracy tradeoff. Participants sacrificed speed for accuracy in that test after exposure, as the improvement was not seen when not subjected to 39.6 degrees. So it seems that the hotter summer temperature could affect the frontal lobe-driven executive function and our perceptual abilities.

But this is not the only area negatively impacted by high temperatures; mental health also suffers.

With the heat, it feels like your brain and mental health are melting

Scorching days affect social interactions and personal well-being, which becomes a threat to mental stability. According to a 2018 study published in Nature Climate Change, a 1-degree Celsius increase in average temperature in the United States and Mexico correlates with a 1% increase in suicides. This data worries if the WMO predictions are accurate and if temperatures will worsen in the coming years, if not in weeks.

Shabab Wahid, a mental health expert at Georgetown University’s Department of Global Health, told Time Magazine that “it’s easy to understand how a traumatic experience like a hurricane can affect mental health. The connection between heat and mental illness is not so intuitive.”

Robin Cooper, an associate clinical professor at the University of California, San Francisco, and president of the Climate Psychiatry Alliance, tells TIME that “we need to start thinking about climate change as a mental health crisis. If we ignore climate change as a public health threat, we are abdicating our role as health care providers.” This means even more research, especially explaining the effect of heat on the exact mechanisms of brain function. Scientists point to many interrelated psychological, social, and biological factors ranging from sleep disruption to the heat-altered role of vital neurotransmitters and hormones.

One of the areas most affected by heat is sleep, especially for those without fans or air conditioning, as it makes quality sleep difficult to achieve. Over time, this can lead to memory loss, lack of concentration, and increased irritability. Also, sleep problems are often related to triggering manic episodes in people with bipolar disorder.

Josh Wortzel, who studies the intersection of climate change, heat waves, and mental health at Brown University, explained to TIME that “heat also affects the neurotransmitter serotonin, one of our most important mood regulators, closely related to keeping aggression under control.”

He says that “serotonin helps relay information about skin temperature to the brain’s hypothalamus, which then controls shivering and sweating responses when necessary. Patients with depression often have difficulties with this process of thermoregulation; The fact that these problems may improve when patients take selective serotonin reuptake inhibitor antidepressants suggests a relationship between heat exposure and serotonin production.”

Still, much remains to be known about how climate change and high temperatures affect mental health, but little financial support exists. Without more knowledge on the subject, it becomes difficult for psychiatrists to know how to prepare and help their patients—especially given that hotter summers are expected and their relationship to suicide.

In addition to all these effects, high temperatures can also cause muscle cramps, exhaustion, nausea, vomiting, fatigue, fever, and heat stroke, which can cause seizures or even death in extreme cases. If you have any of these symptoms, seek help from a health professional.

Translation by Daniel Wetta

Paulette Delgado

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This article from Observatory of the Institute for the Future of Education may be shared under the terms of the license CC BY-NC-SA 4.0